Discover the fascinating exoplanets TOI-791b and TOI-791c, which are roughly the size of Jupiter yet exhibit a remarkably low density—similar to that of cotton candy. This unique combination offers astronomers invaluable insights into the formation and evolution of gas giant planets.
Diagram illustrating the TOI-791b and TOI-791c planets alongside their parent stars. Image credit: NASA/Daniel Rutter.
TOI-791b is comparable in size to Jupiter but possesses only 3% of its mass, while TOI-791c is even larger than Jupiter yet has only 5.9% of its mass.
Both planets orbit TOI-791, a solar-type star located approximately 1,113 light-years away in the constellation Taurus.
As Dr. John Jenkins from NASA’s Ames Research Center stated, “These planets are intriguing to study because their existence was unexpected.”
“They pose an essential challenge for understanding the formation of giant planets like Jupiter and Superpuff.” NASA’s TESS mission played a pivotal role in detecting these exoplanets by observing periodic dips in stellar brightness, indicating a planet crossing in front of its star.
Due to their exceptionally long orbital periods—139 days for TOI-791b and 232 days for TOI-791c—TESS required 1,122 days of observations over seven years to confirm their attributes.
This planetary system serves as a remarkable laboratory to explore the genesis and evolution of superpuff planets, according to Professor Amaury Tryode from the University of Birmingham.
“We aim to utilize NASA/ESA/CSA’s James Webb Space Telescope for space-based observations to investigate the atmospheres for carbon, nitrogen, and oxygen compounds, enhancing our understanding of these extraordinary planets’ formations.”
Comparison of TOI-791b and TOI-791c against planets in our solar system. Image credit: NASA/Daniel Rutter.
TOI-791b and TOI-791c are gravitationally bound to each other, altering their orbital timings due to their mutual attraction.
Astronomers have utilized timing measurements to determine the planets’ masses, revealing their exceptionally low densities.
Dr. George Dunsfield from the University of Oxford remarked, “Finding two super-bulky planets within the same system is a rare occurrence.” Their low densities make these planets particularly compelling for studying the development of planetary systems.
Steve Howell from NASA’s Ames Research Center emphasized, “Further research on these Jupiter-sized yet less massive planets is crucial, as the formation of large planets is believed to shape planetary system evolution.”
Professor Tristan Guillot from the University of the Cote d’Azur stated, “These multiplanetary systems are intricate, with gravitational interactions evolving over extended periods, even decades.”
This groundbreaking research is featured in a recent publication: a paper in the Royal Astronomical Society Monthly Notices.
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Georgina Dransfield and others. 2026. ASTEP identified a pair of long-period, Jupiter-sized planets with extremely low density passing through TOI-791. MNRAS 549 (4): stag864; doi: 10.1093/mnras/stag864
Source: www.sci.news